Basically as the title says. I've got a 87 GTA, rear disc brakes. I know some people have issues with the rears not working, but when I bled mine fluid shot out as good as the fronts did. But when braking, they don't even hit the rotors. I also replaced brake pads back there. I recently did a rear and swap with the same exact rear and they were working fine before this swap. What do you guys think is going on? I know the proportion valve could be a culprit but not so sure with the bleeding results.

You said you did a swap of the rearend. I think 87 still had the iron rear calipers stock, so did you swap the rearend to the aluminum pbr calipers or stay with the same iron calipers?

Nope same style iron calipers. Came from the same year GTA as well. To add, you can see the piston moving but it's not making contact, it's barely moving.

Can you push out the piston by hitting on the brake pedal many times?
How is the condition of the piston seal?

Yes that's what happens but it barely makes contact. The condition of the seals appear to be good. No rips or anything.

Is there a separate backing plate for the pads?

Is the hand-brake mechanism working correctly? It is required to adjust the rear pads.

I'm not sure. I connected everything for it so I don't see why it wouldn't be.

Just did some reading and saw that you do infact have to re-adjust the rear brakes with the e-brake, especially when changing pads. I'd imagine the same when swapping a rear. I'll give this a shot and will update. Hopefully that is all.

Yep.


PARKING BRAKE ADJUSTMENT

1. Apply service brake pedal three times with a pedal force of approximately 175 lbs.
2. Apply and release parking brake three times.
3. Raise car and suitably support.
• Mark relationship of wheel to axle flange.
4. Check parking brake hand lever for full release.
• Turn ignition on.
• "BRAKE" warning lamp should be off
• If "BRAKE" warning lamp is still on, and the hand lever is completely released, pull downward on the front parking brake cable to remove slack from lever assembly.
• Turn ignition off
5. Remove rear wheels and tires.
• Reinstall two inverted lug nuts to retain rotor.
6. Pull parking brake hand lever exactly four (4) ratchet clicks.
7. Parking brake levers (2) on both calipers should be against the lever stops on the caliper housings. If levers are not against stops. check for binding in rear cables and/or loosen cables at adjuster until both left and right levers are against their stops.
8. Tighten parking brake cable at adjuster until either the left or right lever begins to move off the stop, then loosen adjustment until lever moves back barely touching stop.
9. Operate parking brake several times to check adjustments. After cable adjustment is performed, parking brake hand lever should travel 14 clicks. Rear wheels should not rotate forward when hand lever is applied 8 to 14 ratchet clicks.
10. Install wheels and tires, aligning previous marks.
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.
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Have you considered doing the proportioning valve spring mod? Basically, change the spring from the proportioning valve from the stock 10 inlb (i think) to a 19inlb spring. It does help. I have done it on my car, and I have heard that it fixes a lot of rear brake issues.

not to hijack but i have the same issue. new lines, calipers, hardware. when the rear is jacked up, idling in gear brakes fully applied, the rear still spin. pedal is firm, booster holds vac, just no stopping power. i did that whole procedure and bled them many times to no luck. any ideas?

Well good news is I changed the two front brake hoses and my pull is gone. Both were totally blocked. New right rear caliper. Gotta say I like the new design. Bled the brakes and you could see the rears grabbing hard during the bleeding process. Soon as i crank the car and hit the brakes the rears do nothing. Handbrake doesn't even grab em and thats properly adjusted with no brake light on. Was thinking maybe I need to do the proportion spring mod and go from there. Anyone have any ideas as to why they grab when bleeding but not when the car is running?

Did you bleed the rears 1st ??

Did the fronts first actually. Bad move?

Yup.

Well bled the rears again. They are definitely grabbing just nothing extreme. Gonna try the spring mod

You have to un-bleed the fronts b4 you re-bleed the rears or it won't work.

When you say un-bleed the front what do you mean exactly?

I always bleed in this order,

1. Right Rear
2. Left rear
3. Right Front
4. left front
5. Repeat as needed

Crack open the lines or bleeder to ditch the fluid psi while bleeding the rears.
Check the post above mine, hes got it right.

I had the same issue when swapping a 10 bolt drum to a 9 bolt disc. I got all new calipers/pads/master. Still o luck. My new ebrake cables and spring upgrade made all the difference. Mine doesn't pull that high at all though. But the brakes work as they should now.

i ordered and installed the spring at the same i replaced my master cylinder. just with the car jacked up, the rear brakes actually stop now. they used to just drag when it was a stock car, still dragged with a 2400 stall converter. now they actually stop, and well enough the engine stalled when i hit the brakes from 25 on stands. hopefully soon i can get real results on the street

How were your results?

its much better. still working the rust off the rotors, but it stops so much better. it doesnt make me nervous in traffic when people abruptly stop

im gonna give this a whirl and see what happens

I just replaced it and you can feel the difference almost immediately